Measurement of Activities of Human Serum Sulfotransferases Which Transfer Sulfate to the Galactose Residues of Keratan Sulfate and to the Nonreducing End iV-Acetylglucosamine Residues of

Human serum sulfotransferase activities were measured in normal controls and patients with macular corneal dystrophy (MCD), an inherited disorder characterized by the decreased sulfation of keratan sulfate in the corneal stroma and serum, using two kinds of acceptor: partially desulfated keratan sulfate and a trisaccharide with a GlcNAc residue at the nonreducing terminal, GlcNAc£l-3Gal/91-4GlcNAc. When partially desulfated keratan sulfate was used as the acceptor, only sulfotransferase activity which transfers sulfate to position 6 of the Gal residues was detected. In contrast, when GlcNAc#l-3Gal;91-4GlcNAc was used as the acceptor, sulfotransferase activity which transfers sulfate to position 6 of the nonreducing terminal GlcNAc residue could be detected. Although keratan sulfate levels in the sera of MCD patients determined by ELJSA were much lower than those in normal controls, there were no detectable differences in either the sulfotransferase activity responsible for the sulfation of position 6 of Gal residues or that responsible for the sulfation of position 6 of nonreducing end GlcNAc residues between normal controls and MCD patients. These results suggest that the sulfotransferase involved in the sulfation of keratan sulfate, which is assumed to be deficient in MCD patients, may not be secreted into the serum, and that direct measurement of the sulfotransferase activity present in affected tissues such as the cornea instead of serum may be necessary to confirm the postulated deficiency in the biosynthesis of keratan sulfate in MCD